The replication of the myxo-, paramyxo, rhabdoviruses is independent of host cell DNA function and takes place in the presence of actinomycin D. The single-stranded RNA viral genome is transcribed into a complementary RNA which serves as messenger RNA for the viral protein synthesis. This synthesis of complementary RNA is performed by an RNA-dependent RNA polymerase that is found in the virion itself. Later, in the infectious process, RNA of the same complementarity as the virion RNA is produced and packaged in the progeny virus particles. The details of the mechanism underlying the synthesis of RNA of both complementations senses and the regulation and coordination of these syntheses with each other are the subject of this project.